Bonded glass fiber mats can be made from either short chopped fibers or long, essentially continuous fibers or mixtures of both short and long fibers. The fibers may originally, i.e. before matting and bonding, be present as individual filaments or a plurality of individual filaments may have been gathered together into multi-fiber strands. Furthermore, the fibers may have been provided with a very light coating of a sizing composition before being deposited to form the mat and having the binder composition applied, the function of such sizing (if any) being to protect the fibers from abrasion and consequent weakening during subsequent handling and/or to provide a more adherent substrate for the binder.
Previously, and particularly where glass fiber mat has been formed from multi-fiber strands, binder compositions comprising aqueous dispersions of phenol-formaldehyde or phenol-formaldehyde-urea resins, starch, bone glue, dimer acid and an organosilane have been found to be most suitable for many purposes, e.g. where the mat is to be saturated with asphalt and used as a roofing material. However, bone glue is not always readily available at reasonable cost and it is notoriously variable in quality, thereby introducing an undesirable variability into both the binder composition and the mat bonded therewith.